Integrated Optimal Design for Hybrid Electric Powertrain of Future Aircrafts

Abstract

This paper presents the integrated optimal design of the powertrain of a hybrid regional aircraft using multidisciplinary design optimization (MDO). The sizing of the main components of the propulsion chain is performed over the flight mission under various scenarios regarding energy management strategies and technological assessments. For that purpose, a complete set of multidisciplinary surrogate models are integrated into the MDO process, taking account not only of the main electrical, thermal and mechanical aspects but also of environmental constraints such as partial discharges in electric motors regarding flight conditions. Several MDO formulations are investigated comparing local (i.e., motor mass minimization) and global optimizations (i.e., powertrain mass then fuel burn minimization at aircraft level). Results emphasize main systemic couplings showing that despite future technological progress, the series hybrid architecture is heavier than a conventional thermal aircraft. Nevertheless, thanks to the whole aircraft optimization, potential gains related to kerosene consumption can be reached, reducing the environmental footprint. The “energy gains” focused on in this paper may be added with aerodynamic gains potentially involved in more electric powertrain. This work has been carried out in the frame of the HASTECS project under the Clean Sky II program which aims at reducing CO2 emissions and environmental impacts of the aviation sector.

A Review of Powertrain Electrification for Greener Aircraft

“…However, hydrogen solutions for fuel cells ICEs (internal combustion engines) should also be considered to progress towards greener aircraft, as announced by Airbus with its three zero-emission-aircraft concepts (Turboprop @100 pax-1000 nm, Turbofan @ 100 pax-2000 nm, and Blended wing body @ 200 pax-2000 nm). The reader can find a more detailed report on the state of the art in hybrid-electric and full-electric aircraft concepts in [14]. United Technologies Advanced Projects (UTAP) linked with UTC Aerospace has embarked on the electrification of aircraft with a parallel hybrid powertrain including a downsized (50%) gas turbine associated with a 1 MW auxiliary electric source.…”

“…These progress have to be integrated into hybrid-electric and full-electric powertrains in order to enhance aircraft performance, especially efficiency. Electric solutions reduce fossil source demand and lower aircraft greenhouse gas emissions and the environmental footprint of future aircraft [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. A review of the technological challenges hampering the road toward more electric aircraft powertrains is proposed in [27].…”

“…aircraft concepts (Turboprop @100 pax-1000 nm, Turbofan @ 100 pax-2000 nm, and Blended wing body @ 200 pax-2000 nm). The reader can find a more detailed report on the state of the art in hybrid-electric and full-electric aircraft concepts in [14].…”

“…The research involvement in the HASTECS project is illustrated in Figure 14. -Highly integrated power electronics [48,49] and their high-performance cooling [50,51]; -Highly integrated electric motor [44,45] and its high-performance cooling [42,43]; -Facing environment constraints due to high power/voltage: partial discharges [46,47]; -Prospects towards high-energy-density batteries and fuel cells [52]; -Integrated optimal design of the powertrain [14,68].…”

AC Electric Powertrain without Power Electronics for Future Hybrid Electric Aircrafts: Architecture, Design and Stability Analysis

“…Therefore, to contribute to the weight reduction, the idea of the architecture studied in this paper is to connect the permanent magnet synchronous machines through an AC bus without using power electronics. Indeed, taking as an example the specific power values mentioned in the framework of the European HASTECS project [21,22], on an electric propulsive chain of 500 kW, a decrease in the weight of the chain by more than 30 kg for each power electronics can be foreseen by 2025 (with specific power of 15 kW/kg) and still 20 kg by 2035 (with specific power of 25 kW/kg). Considering the implementation of the single propeller powertrain studied in this paper in an aircraft with two power channels (one for each wing), the previous figures have to be multiplied by four, decreasing the propulsive system weight by 130 kg by 2025 and still by 80 kg by 2035.…”